基于Herschel-Bulkley流变模型的 盾构螺旋输送机保压性能

为准确预测土压平衡式盾构螺旋输送机的保压性能,假定渣土为黏塑性流体材料,对螺旋输送机的进出口压差进行了理论分析,从能量转化的角度解释了保压能力的来源.采用计算流体力学模拟方法对螺旋输送机内渣土的运输进行了定常流计算,其中Herschel-Bulkley模型用于描述渣土材料的流变行为,且运用多重参考系法充分考虑了螺旋叶片的旋转作用,得到了渣土流变参数及螺旋输送机工作参数对保压性能的影响规律,并将模拟结果与室内模型试验结果进行了对比.研究表明:渣土的屈服应力、黏度指数及幂律指数越大,螺旋输送机保压性能越优异,其中黏度指数及幂律指数的影响较为明显;螺旋输送机机械能损失量与螺旋转速和出渣效率基本成正比,转速越快,出渣效率越高,则保压性能越优异,可用二元线性回归模型估测机械能损失量与螺旋转速和出渣效率之间的关系;模拟结果与试验结果的趋势基本一致,Herschel-Bulkley流变模型用于计算螺旋输送机保压性能基本可靠,但模拟结果对保压性能的预估偏保守.基于数值计算结果,提出了螺旋输送机保压性能的优化流程.

Pressure Maintaining Performance of Shield Screw Conveyor Based on Herschel-Bulkley Rheological Model

In order to give a better prediction of the pressure maintaining performance of shield screw conveyor with earth pressure balance, the pressure difference between inlet and outlet of screw conveyor was analyzed on the assumption that the conditioned soil is a viscoplastic fluid, and the pressure maintaining mechanism was explained from the perspective of energy conversion. A steady calculation of the flow state of conditioned soil in screw conveyor was carried out by using computational fluid dynamics (CFD) method, where Herschel-Bulkley model was used to describe the rheological behavior of conditioned soil, and the rotation of screw blade was fully considered by using multi-reference frame (MRF) method. The influence of soil fluid parameters and the working parameters of screw conveyor on pressure maintaining performance was obtained, and a comparison between the simulation results and the indoor test results was carried out. The analysis result shows that the pressure maintaining performance of screw conveyor increases with the increase of yield stress, viscosity index and power-law index, where the influence of viscosity index and power-law index is more obvious. The mechanical energy loss of screw conveyor is basically proportional to the rotating speed of screw and soil removal efficiency. Fast rotating speed and high soil removal efficiency result in excellent pressure maintaining performance. The relationship between the mechanical energy loss, rotating speed and soil removal efficiency can be estimated by using binary linear regression model. The trend of simulation results is consistent with the indoor test results, and the Herschel Bulkley rheological model can be used to calculate the pressure maintaining performance of screw conveyor. However, the prediction of pressure maintaining performance is conservative. Finally, based on the results of numerical calculation, the optimization process of screw conveyor pressure maintaining performance is proposed.